1. Field of the Invention
The present invention relates to a speaker with a built-in filter used for a digital amplifier, and more particularly, to a speaker with a built-in filter capable of being connected directly to a digital amplifier.
2. Description of the Related Art
Advancement in digital technology has led to an increase in use of digital devices capable of playing back multimedia data. Recently, digital amplifiers are being employed in digital devices, thereby making it possible to manufacture smaller and lighter digital devices. A digital amplifier (full digital amplifier) amplifies an audio signal in digital form. By amplifying the audio signal in digital form, the digital amplifier is capable of reducing signal distortions compared to an analog amplifier. Further, the digital amplifier is more efficient and easier to be miniaturized than the analog amplifier.
FIG. 1 schematically illustrates a digital amplifier 10, a low pass filter 20 and a speaker 30 according to a prior art. Referring to FIG. 1, the digital amplifier 10 amplifies an input audio signal, and outputs the amplified audio signal to the low pass filter (LPF) 20. The low pass filter 20 converts the amplified audio signal into an analog signal, and outputs the analog signal to the speaker 30. The speaker 30 outputs the analog signal as an audio signal.
Generally, the low pass filter 20 requires an inductor and a capacitor. The inductor is bulky and heavy, which makes it difficult to manufacture smaller and lighter digital devices.